Tissue engineering of a bioprosthetic heart valve: stimulation of extracellular matrix assessed by hydroxyproline...

Creation of an autologous heart valve by tissue engineering offers a promising approach to cardiac surgery. Although we have demonstrated successful formation of native valve analogous tissue in vitro, hemodynamic competence remains a serious problem. The aim of this study was to optimize in vitro formation of collagen as a precondition for mechanical stability of new tissue. Human myofibroblasts were seeded on square sheets of biodegradable scaffolds (control). To stimulate collagen production, one series was cultured with L-ascorbic acid 2-phosphate. In a second series, the seeded scaffolds were subjected to tension by mounting them on a frame. After 4 weeks of culture time, the collagen content of the different series was assessed by hydroxyproline assay. Light and scanning electron microscopy were performed. Hydroxyproline content of the framed scaffolds was 10 times higher than that of the control group (p < 0.05) and 6 times higher than in the unframed scaffolds grown with ascorbic acid (p < 0.05), respectively. Scanning electron microscopy proved extensive formation of solid tissue in the framed samples. These results demonstrate that supplementation of myofibroblast cultures with ascorbic acid, especially if grown on strained scaffolds, significantly increases collagen content, which is crucial for mechanical stability. This concept is a further step toward the creation of a hemodynamically competent autologous heart valve.